Make break contact material comprising ag-ni based alloy having ni metal particles dispersed and relay using the same

ABSTRACT

A make-and-break contact material which is less worn out and is able to achieve an increased life compared to a conventional material of Ag—CdO-based alloy, in an AC general relay used for a resistive load of about 1 to 20A in a range of AC 100V to 250V. In the present invention, the make-and-break contact material of Ag—Ni-based alloy used for a switching part performing electrical switching through mechanical switching operation is the make-and-break contact material of Ag—Ni-based alloy with Ni metal particles dispersed therein which is obtained through mixing and stirring 3.1 to 20.0 wt % of Ni powder, a certain amount of Li 2 CO 3  powder corresponding to 0.01 to 0.50 wt % of metal Li as an additive, and a balance being Ag powder to make a mixture with the above described powders uniformly dispersed therein, and through compacting and sintering the above described mixture.

This application is a national stage entry of International ApplicationNo. PCT/JP01/06219, filed Jul. 18, 2001 designating the U.S., whichclaims the benefit of Japanese Application No. 2000-220360, filed Jul.21, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to increasing durability of an AC generalrelay and specifically, in the AC general relay used for a resistiveload of about 1 to 20A in the range of AC 100V to 250V, to amake-and-break contact material of Ag—Ni-based alloy with Ni metalparticles dispersed therein having excellent endurance compared to aconventional make-and-break contact material of Ag—CdO-based alloy andto a relay using the same.

2. Earlier Technology

An electric contactor which is used for a switching part performingelectrical switching through mechanical switching motion is generallycalled an electric contact. The electric contact requires to transmit acurrent and signals passing through the contact without any trouble bymetal-to-metal contact and to allow itself to be in an open positionwithout any trouble when the metal-to-metal contact is disengaged.

The electric contact has a simple structure, however, it has becomecommon-sense that various physical or chemical phenomena occur on asurface of the contact. The phenomena include, for example, adsorption,oxidation, sulfurization, synthesis of organic compounds, and further,melting, evaporation, ablation, and conversion which entail discharge.These phenomena are significantly complicated and have not yetacademically clarified in many parts, and are greatly attributed to thequality of the electric contact material.

Upon occurring these phenomena, a contact function of an electriccontact is somewhat disrupted and in some cases the contact function iscompletely disrupted (e.g., welding), which determines performance anduseful life of an electrical appliance incorporating the electriccontact. This means that the electric contact is one of the importantparts which determine the useful life and performance of the electricalappliances or the like.

In recent years with the significant advancement of electronics andelectrical engineering, the scope of application of the electric contactwidely varies from an electronic field including a telegraph andtelephone and other various electronic equipment to an electric fieldincluding electric equipment which interrupts a large current.Therefore, functions to be required vary widely, so that the developmentof the electric contacts having characteristics adapted to theirrespective uses is now in progress, and great many kinds of electriccontacts are supplied to the market.

In such an electric contact, the technical common-sense having beenconventionally known of the AC general relay or switch which is asubject matter of the present invention is as follows. That is, theelectric contactor incorporated in the relay or switch is a so-calledmake-and-break contact. An electric contact material used for thismake-and-break contact is in particular required to have wear resistanceand transition resistance in order to maintain a stable mechanism andlow contact resistivity in order to maintain a stable contact state.

Make-and-break contact materials used for the AC general relays or thelike, which are traditionally well known, include an Ag—CdO-based alloy(an alloy comprised of 10 to 15 wt % CdO and a balance being Ag) or thelike.

Although each of these electric contact materials may be used alonewithout being processed, the material may frequently be used after beingprocessed into a two or three layered-type of clad rivet contact inwhich this material is laminated on Cu or a Cu alloy as a primer or intoa two to five layered-type of clad crossbar contact in which thismaterial is laminated on Cu or a Cu alloy as a primer. This clad rivetcontact or clad crossbar contact is used being incorporated in therelays, in which electric signals applied in a form of a direct current,an alternating current, or electric impulses generate a coil magneticflux, and the magnetic force attracts a moving iron, then the electriccontact performs switching operations responding to the motion of themoving iron.

This conventional Ag—CdO-based make-and-break contact material satisfiesthe wear resistance, the transition resistance, and the low contactresistivity at practical levels when using the alternating current loadranging from AC 100 V to 250 V, however, it has been newly pointed outthat this material has following problems.

First of all, the conventional make-and-break contact material is not amaterial adapted to a requirement of a miniaturization. With theenhancement of the functions and performances of the householdelectrical appliances, the numbers of electric parts to be mountedincrease and the miniaturization of the parts themselves is furtherproceeding. Thus, in spite of being desired to achieve theminiaturization of the relays or switches themselves in consideration ofthe cost, the conventional make-and-break contact materials cannotsufficiently address the miniaturization.

In other words, if a volume of the make-and-break contact materialbecomes smaller in order to achieve the miniaturization of the relays,the work load per unit volume of the material largely increases at thetime of conduction and interruption of the current, and consequently,the conventional material itself is rapidly worn out, then the failuresoccur at early stage.

SUMMARY OF THE INVENTION

The present invention is developed against the background of the abovedescribed circumstances and to provide a make-and-break contact materialwhich is able to achieve the less wear and to-increase the useful lifeof the AC general relays even when the miniaturization is achieved,compared with a conventional Ag—CdO-based material.

The inventors have devoted themselves to this development in order tosolve above described problems and finally found a make-and-breakcontact material of Ag—Ni-based alloy with Ni metal particles dispersedtherein as follows. That is the make-and-break contact material ofAg—Ni-based alloy which is used for a switching part performingelectrical switching through mechanical switching motion, wherein thematerial with Ni metal particles dispersed therein is obtained by mixingand stirring 3.1 to 20.0 wt % of Ni powder, a certain amount of Li₂CO₃powder corresponding to 0.01 to 0.50 wt % of metal Li as an additive,and a balance being Ag powder to form a mixture with the above describedpowders uniformly dispersed therein, and by subjecting the abovedescribed mixture to a compacting process and to a sintering process.

The make-and-break contact material of the present invention is anAg—Ni-based alloy with Ni metal particles dispersed in an Ag matrix andwith Li₂CO₃ dispersed therein. According to the make-and-break contactmaterial of Ag—Ni-based alloy with Ni metal particles dispersed thereinof the present invention, wear resistance, transition resistance, andlow contact resistivity are maintained at practical levels in case of anAC load of 1 to 20A in a range from AC 100V to 250V, even when a volumeof the make-and-break contact material itself becomes smaller.Consequently, it becomes possible to achieve long-term usage, i.e. theincrease in its useful life.

Ni in the make-and-break contact material of Ag—Ni-based alloy with Nimetal particles dispersed therein according to the present inventionexists as Ni metal particles in the Ag matrix and contributes toimprovement of wear resistance when the material is used for an ACgeneral relay in the range from AC 100V to 250V and from 1 to 20A. Whenthe amount of Ni is less than 3.1 wt %, it becomes difficult to maintainwear resistance of the AC general relay to the practical level, whilethe amount of Ni exceeds 20.0 wt %, then the problems associated withmanufacturing the contacts such as reduction in stability of contactresistance and in workability will occur. In the case of using thismaterial for the AC general relay, it is optimum that the Ni powder inthe make-and-break contact material of Ag—Ni-based alloy with Ni metalparticles dispersed therein according to the present invention is 8.0 to15.0 wt %.

Li₂CO₃ also exists as particles in the Ag matrix as in the case of Nimetal particles, and in an application for the AC general relays used inthe range from AC 100V to 250V and from 1 to 20A, the present materialexhibits arc extinguishing action similar as that of the conventionalCdO and contributes to improvement of wear resistance. However, when themetal Li is less than 0.00 wt %, the effect of Li₂CO₃ cannot berecognized, while the metal Li exceeds 0.50 wt %, the stability ofcontact resistance is reduced and the sintering property of the materialis also degraded. Thus, it becomes difficult to manufacture thisproduct. When using this material for the AC general relays, Li₂CO₃powder in the make-and-break contact material of Ag—Ni-based alloy withNi metal particles dispersed therein according to the present inventionis optimally exists in the amount of 0.05 to 0.2 wt % on a metal Libasis.

When constituting the relay using the make-and-break contact material ofAg—Ni-based alloy with Ni metal particles dispersed therein according tothe present invention, miniaturization of the relay is achieved and wearresistance, transition resistance, and low contact resistivity aremaintained at practical levels in case of using the AC load in a rangefrom AC 100V to 250 v and from 1 to 20A. Therefore, it becomes possibleto achieve long-term usage, i.e. the increase in its useful life.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the data obtained from endurance tests areplotted on a Weibull probability paper; and

FIG. 2 is a graph showing investigation results on wear resistanceaccording to ASTM tests.

PREFERRED EMBODIMENTS

An embodiment of the present invention will be explained with referenceto the examples described below. Example 1 described in Table 1 is amake-and-break contact material of Ag—Ni-based alloy with Ni metalparticles dispersed therein according to the present invention,Conventional Example 1 is a conventional make-and-break contact materialof Ag—Ni-based alloy, and Comparative Example 1 is a make-and-breakmaterial mainly used for a general relay.

TABLE 1 Li₂CO₃ powder being added Ag powder Ni powder (as metal Li)Example 1 Balance 10.0 0.1 Conventional Balance 10.0 — Example 1 Ag CdOComparative Balance 12.0 Example 1

The make-and-break contact material of Ag—Ni-based alloy with Ni metalparticles dispersed therein according to Example 1 was made into acylindrical powder compact by mixing 10.0 wt % of Ni powder, a certainamount of Li₂CO₃ powder corresponding to 0.1 wt % of metal Li as anadditive, and a balance being Ag powder, stirring this powder mixturefor four hours in a ball mill to make the mixture uniform, then loadingthe mixture within a cylindrical vessel, and applying pressure to thismixture in a longitudinal direction of the cylindrical vessel. Followingthis compression process, a sintering process was carried out for fourhours at 1123K (850° C.). These compression process and sinteringprocess were repeated four times. A billet subjected to the compressionprocess and sintering process was formed into a wire having a diameterof 6.0 mm through hot extrusion. Subsequently, the wire was subjected towire drawing to have a diameter of 2.3 mm. Then the 2.3 mm-diameter wirewas-made into a rivet contact having a head diameter of 3.5 mm and ahead thickness of 1 mm using a header machine.

In Conventional Example 1, a rivet contact was also made by the sameprocess as that in Example 1, except for adding Li₂CO₃.

On the other hand, Comparative Example 1 was about a make-and-breakcontact material formed by the so-called internal oxidation process,which is currently and mainly used for a general relay. A wire was madefrom this material, and a rivet contact having a head diameter of 3.5 mmand a head thickness of 1 mm was made by a header machine as describedin Example 1 and Conventional Example 1.

Each rivet contact was incorporated into the AC general relay and anendurance test was performed in accordance with the conditions describedin Table 2. This endurance test was performed using five or more relays,the numbers of switching until respective relays fail (service life) areshown in Table 3 and each result which is represented on a Weibullprobability paper is shown in FIG. 1. In addition, Table 4 showscharacteristic life values, m-values, and the numbers of switching at 5%of cumulative failure rate, all of which are read from the Weibullprobability paper.

TABLE 2 Voltage AC 250 V Current 10 A Load Resistance Switchingfrequency 1.0 sec. ON/2.0 sec. OFF Contact force 4.41 × 10⁻¹N (45 gf)Opening force 4.41 × 10⁻¹N (45 gf) Ambient temperature Ordinarytemperature

TABLE 3 Conventional Comparative Example 1 Example 1 Example 1 Numbersof 905,126 199,652 643,165 switching 963,843 387,089 659,002 duringservice 986,753 548,444 690,004 life 1,020,587   594,609 694,7001,044,980   657,233 753,545 — — 810,871 — — 870,051 — — 881,826

TABLE 4 Value of Numbers of switching characteristic at 5% of cumulativelife m-value failure rate Example 1 1,009,336   18.6 860,397Conventional 599,027 2.1 132,004 Example 1 Comparative 793,053 8.3554,128 Example 1

According to the result of endurance test shown in Table 3, themake-and-break contact material of Ag—Ni-based alloy from this Example 1was verified that the material had an service life of 900,000 times ormore of switching when using a resistive load of 10A at AC 250 V.Conventional Example 1 shows that the first relay failed when thenumbers of switching reached to about 200,000, so that an effect ofadding Li₂CO₃ described in the present invention was verified. On theother hand, the first relay from Comparative Example 1 failed when thenumbers of switching reached to 640,000. Therefore, it was also verifiedthat the relay from Example 1 had a longer service life than that of therelay from Comparative Example 1 which had currently become a standardof the AC general applications, so that the material from Example 1 wasexcellent.

As can be seen from comparing respective data with each other which areread from the Weibull probability paper shown in Table 4, it has beenfound that the relay from Example 1 has a large characteristic lifevalue and a large m-value, so that this relay is excellent in its usefullife characteristic and is stable without variations in a failureprobability. As for the numbers of switching at 5% of cumulative failurerate, the relay from Example 1 has the largest value, so that this relayis found to have practically excellent endurance.

A result of investigating the wear resistance according to ASTM test isnow described. This ASTM test is performed by using the rivet contactdescribed above, carrying out switching operation in accordance with theconditions described in Table 5, and then measuring a decreasing weightof the contact as an amount to have been worn out. The result isdescribed in FIG. 2.

TABLE 5 Test voltage AC 250 V Test current 10 A Load ResistanceSwitching frequency 0.5 sec. ON/0.5 sec. OFF Contact force 8.33 × 10⁻¹N(85 gf) Opening force 8.33 × 10⁻¹N (85 gf) Numbers of switching 150,000times

As shown in FIG. 2, a worn-out amount in Example 1 was 0.620 mg onaverage, while the worn-out amount in Conventional Example 1 was 0.846mg on average, and the worn-out amount in Comparative Example 1 was0.894 mg on average, so that it has been verified that the relay fromExample 1 is definitely excellent in the wear resistance.

As for the make-and-break contact material of Ag—Ni-based alloy with Nimetal particles dispersed therein according to the present invention, ithas been verified that an breakthrough improvement has been recognizedin a resistive load of an AC general relay, the useful life as the ACgeneral relay can be significantly increased. These improvements allowthe above described material to respond to the further miniaturizationof the AC general relays and to the increase in its useful life of therelays.

What is claimed is:
 1. A make-and-break contact material comprising anAg—Ni-based alloy comprising 3.1 to 20.0 wt % of Ni, Li₂CO₃ in an amountcorresponding to 0.01 to 0.50 wt % of Li metal, and a balance of Ag. 2.A relay comprising the make-and-break contact material of claim
 1. 3. Aswitching part comprising the make-and-break contact material of claim1, wherein said switching part performs electrical switching through amechanical switching operation.
 4. A make-and-break contact materialaccording to claim 1, wherein said contact material comprises 8.0-15.0wt % of Ni.
 5. A make-and-break contact material according to claim 1,wherein said contact material comprises Li₂CO₃ in an amountcorresponding to 0.05 to 0.2 wt % of Li metal.
 6. A make-and-breakcontact material according to claim 1, wherein said Ni powder isuniformly dispersed in said Ag-Ni-based alloy.
 7. A make-and-breakcontact material according to claim 1, wherein said Ag powder is presentin an amount that constitutes the balance of said alloy.
 8. Amake-and-break contact material according to claim 1, wherein saidcontact material is adapted to withstand at least 900,000 times or moreof switching when using a resistive load of 10A at AC 250V.
 9. Amake-and-break contact material according to claim 8, wherein saidcontact material is part of a miniaturized make and break contact.